Science MCQ Questions with answers

Explanation:

Saltwater is the best conductor of electricity because it contains dissolved ions (such as sodium (Na⁺) and chloride (Cl⁻)), which facilitate the flow of electric current. In contrast, distilled water is a poor conductor because it lacks these ions. Filtered water at room temperature may contain some impurities, making it a weak conductor. Filtered hot water can have slightly better conductivity than cold water, but it is still not as effective as saltwater.

When an electric current is passed through saltwater, the dissolved ions move freely, allowing the electricity to flow efficiently. This principle is widely used in applications like electrolysis and batteries. Thus, among the given options, saltwater is the best conductor of electricity.

Explanation:

When two cars pass each other at high speed, the air between them moves faster due to the Bernoulli’s Principle, which states that an increase in the speed of a fluid (in this case, air) results in a decrease in pressure.

As the velocity of air molecules between the cars increases, the air pressure in that space decreases. Meanwhile, the pressure on the outer sides of the cars remains higher. This pressure difference creates a force that pushes the cars toward each other, increasing the risk of a side swipe or collision.

This effect is commonly observed in racing cars, trains, and even in ships passing close to each other.

Explanation: Pellagra is a disease caused by low levels of niacin, also known as vitamin B-3. It's marked by dementia, diarrhea, and dermatitis, also known as “the three Ds”.